Method of and apparatus for amplification at different frequencies



April 16, 1929.

s. COHEN 1,709,062

METHOD OF AND APPARATUS FOR AMPLIFICATION AT DIFFERENT FREQUENCIES Filed Dec. 19. 1922 II 1 lg 2 Lllmfil T We Ca P2 \C6' .9 :1 j If PF 7 Ta 1/02 64 L y 1 W 9 T A B W1 2 MIIIM F2 RI-MI l N VEN TOR.

A M BY M35121? ATTORNEY.

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Patented Apr. 16, 1929.

SAMUEL COHEN, F BRQOKLYN,'NEW YDRK,

METHOD OF AND APPARATUS FOR AMPLIFICATION AT DIFFERENT.

Application filed December 19, 1922. fierial No. 60?,776.

My invention relates to a method of and apparatus for amplifying fluctuating, alterhating or oscillatory current, such, for example, as received in radio or high frequency signaling systems for purposes of telephony, telegrapl iy and signaling in general. a

in accordance with my invention, the high or radio frequency current is first amplified, as by a thermionic amplifier; the amplified current is then rectified by any suitable type of rectifier, as a crystal detector, thermionic rectifier, or the like, and the rectified current is then amplified at lower or audio frequency by the same device or thermionic amplifier which amplifies the incoming current at radio or other high frequency.

My invention resides in the method and apparatus of the character hereinafter described and claimed. I

For an understanding of my method, and for an illustration of some of the various forms of apparatus embodying, my invention,

reference may be had to the accompanying drawin in which:

Fig. l is a diagrammatic view of apparatus in accordance with my invention, involving a transformer coupling between amplifier and rectifier.

Fig. 2 is a diagrammatic view of apparatus embodying my invention, in which the amplifier and rectifier are coupled by an inductance or auto-transformer.

Fig. 3 is a diagrammatic view of apparatus embodying my invention in which the amplifier and rectifier are coupled by a resistance.

Fig. 3 is a fragmentary diagrammatic view illustrating a thermionic rectifier which may be utilized as the rectifier of any of the arrangements of Figs. 1, 2 and 3.

Fin. 4 is a diagrammatic view of a modificd form of my invention in which the rectifier is of the thermionic type and disposed in the same vacuum with the thermionic amplifier.

Referring to Fig. 1, A represents an an tenna or other absorption structure, or a con ductor upon which exist high frequency oscillations. as of radio frequency. representing telephonic, telegraphic or other messages or signals. Between the antenna A and the earth or counter-capacity E is connected the primary P of an oscillation transformer and a variable condenser G for tuning the antenna path to the frequency of the received energy, it being understood that condenser the variable condenser C for tuning ondary circuit to the frequency of the received energy. One terminal of the secondary circuit is connected to the control, electrode, or other control means, as the g .d 7 of the vacuum tube or thermionic a V, having in addition to the grid the node a; and the cathode or filament f, the latter supplied by current from the belt 7 l; in quan tity controllable by the van unce or rlieostat r. are sec- The other terminal CH. ondary is connected through the corulcnser C with the cathode or filament t The vac uum tube V is of the so-ca .1. t and is preferably of the t electron discharge, as who in the tube V is extremely in the anode circuit a tery or source of current cciver T, shunted by the condc by-passcs the high. frequency on .nt around the telephone T, and the primary P of a radio frequency transformen preferably shunted by the variable condenser C for tuning the circuit to the frequency of the re ceived energy. In inductive relation to the primary P is the secondary S of the radio frequency transformer, preferably shunted by the variable condenser C for tuning the circuit to the frequency of the received energy. In series with the secondary El is a rectifier R, of any suitable type. here indicated as a so-callcd crystal rectifier or detector. such as galcna. silicon, etc. in contact with another conductor, or one employing copper pyrites in. contact with zincite. In series with the rectifier R is the primary P of a low or audio frequency transformer whose secondary is bridged across the aforesaid condenser T, which exhibits low reactance for lay-passing the received high frequency oscillations around the secondary S A condenser C is preferably bridged across the primary P for by-pnssing the high frequency oscillations from the second ary S around the primary P By thermionic amplifying action, well undcrstood in the radio art, the incoming high or radio frequency current is amplified by the thermionic device V, the amplified high frequency current appearing in the anode circuit and therefore traversing the primary P and findenser C. By transmitter action hi the bathone re- C which the secsimilar amplified high frequency currents appear in the secondary S, and this amplified current of high or radio frequency is rectified by the device R, there appearing in the circuit of the primary P'a currentlof lower or audio frequency corresponding with the modulation in-= accordance with speech orarv S im rcsses u on the rid circuit of the amplifier V correspondingly high potentials at amliofifrequency, causing amplification at audio frequency by the same thermionic amplifier V of the audio frequency current which a pears in the anode circuit of the amplifier V traversing the telephone-T, and there reproducing speech or other signal as a result of double amplification, that is, am: plification atboth radio and audio frequencles.

In-Fig. 2,1 the arrangement is in general similarto that of 1, except in lieu of the transformer P, S there is utilized the high impedance or inductance L is-series in the anode circuit with the telephone T. The radio frequency inductance or impedance L couples the anode circuit to the circuit of the rectifierR. Tlie rectifier eircuitis in shunt to the impedance L and comprises the condenser C", the rectifier R and theprimary P in series with each other, the condenser C" being of'low reactance for the amplified high or radio frequency current.

The high or radio frequency current is amplified by the thermionic amplifier V, the amplified current appearing in the anode circnit-and traversing the inductance L and the condenser C The amplified current is transferred to the rectifying. circuit, where it is rectified, and the low or audio frequency current by the transformer P S again varies the potential of the grida-t the low or audio frequency, with the result that the audio frequency current is amplified by. the

same thermionic detector V.

In Fig. 3 the arrangement is in general similar to that .of Fig. 2, except that in lieu of'inductance L is employed a high non-inductive or other suitable resistance Z for effecting a. resistance coupling between the anode circuitv of' theamplifier V and the rectifier circuit, transferring to the latter the amplified high. or radio frequency current. In this case again, amplification is double in the sense that there is an amplification first at high or radio frequency and then at lower or. audio frequency- Any suitable type of rectifier may be utilized atRinthe arrangement of Fig.1, 2

and3. A thermionic rectifier may be;em-

ment beingsupplie ployed, such,.for example,.as indicated at i"; 3, the same comprismg-amevacuated bulb D havin the incandescent cathode or filament f an the late or anode a, the filad with current from a battery 1) controlled 1) a rheostat r. The anode a and cathode; are connected in series in the rectifier circuit in place of the rectifiers Rof Figs. 1, 2 and 3.

In the arrangement of Fig.- 4, the amplified high or radio frequency current in the circuit of the anode a traverses the primary P of the radio frequency transformer, preferably shunted by the tuning condenser C, and the condenser C by-passing-the telephone receiver T.

In this instance the thermionic amplifier is provided with a second anode a, connected through the secondary S of the oscillation,

trans ormer and the primer 1, and a suitable portion of the battery with the cathode f, The-secondar S is preferably shunted by the condenser (l for tuning to the high or radio frequency.

The amplied high or-radio fr uency-current'appearin ,in the secondary k 1 is rectified b the t ermionic action between the catho e f and the anodea', the path between these electrodes -beingasymmetrically conductin There accordin 1y flows thron the. prlmary P a-rectifie current and t e low or audio frequency component impresses a low or audio fr'equenc potential upon the grid g, with the result t at there appears in the circuit of the anode a and telephone T an amplified low or audio frequency current which is translated into a message or signal by the telephone T.

As to Figs. 1, 2, 3 and 4, it will be understood that the telephone T may be replaced by a primary winding of an audio frequency transformer of one or an suitable. number of further stages of ampli cation.

It will be understood as to condensers C in Figs. 1, 2 and 4 and the condenser C in Figs. 1 and 4, that the are preferably. used.f0r tuning purposes, ut that they may be dispensed with, articularly if the. transformer windings P, S of Figs. land 4, or the inductance Lof Fig. 2,. are suitably proportioned or designed, especially when the. frequency of the received energy lies within a relatively narrow range of frequencies. For reception of so-called short waves, these condensers may be. omitted, particularly when the windings P, S of Figs. 1 and 4 and theinductance L of Fig. 2 are so constructed or wound as to have a minimum of distributed capacity.

It is further desirable, as regardsthe windings P, S of the audio frequency transformers of Figs. 1 to 4 inclusive, that they should have hi h inductance values and small. or negl i 'ble distributed ca acity, to I enhance trans ormation between 2 ends at audio frequencies only.

In Fig. 2 the circuit L, C is an anti-resoinfinite impedance. The condenser C shunting the iductance L may in some instances be omitted, particularly in case the induct ance-L exhibits high inductance and has low or negligible distributed capacity.

The degree of vacuum within the amplifier tube V is of importance in that when the tube is soft, that is, when the tube contains rarified gaseous medium, the double amplification of the character described is not nearly so effective, if at all effective, as in the case when the tube is hard, that is, when the tube contains practically no gas and the discharge is a pure or substantially pure electron discharge.

What I claim is:

1. The combination of an electron tube system having a cathode, an anode and a control electrode arranged in the order named, an auxiliary anode mounted adjacent said cathode opposite said first mentioned anode and control electrode, an input circuit including said cathode and said control electrode, an output circuit including said first mentioned anode and said cathode and a separate circuit inductively coupled to each of said circuits and connected with said auxiliary anode, a responsive device connected in said output' circuit, said first mentioned anode, control electrode and cathode cooperating for the amplification of'incoming signaling energy at different frequencies and said auxiliary anode and cathode cooperating to rectify the incoming signaling energy.

2. The combination of an electron tube system comprising an evacuated vessel, a pair of anodes, a cathode and a control electrode, an input circuit interconnecting said cathode and control electrode, an output circuit including one of said anodes and said cathode in series with a loop resonant circuit and a responsive device connected therein, a series circuit connected between a point of high potential in said output circuit and said other anode, said series circuit including a loop resonant circuit electromagnetically coupled with said first mentioned loop resonant circuit, said first mentioned anode, cathode and control electrode cooperating for the amplification of incoming signaling energy at different frequencies and said second mentioned anode and cathode cooperating to rectify the incoming signaling energy for actuating said responsive device.

3. The combination of an electron tube system comprising an evacuated vessel, a pair of anodes,- a cathode and a control electrode, an input circuit interconnect-ing said cathode and saidcontrol electrode, an output circuit interconnecting said cathode and said other anode, said output circuit including a tuned circuit, a responsive device and a source of potential, an auxiliary circuit including a tuned circuit coupled with said first mentioned tuned circuit and connected at one end with said other anode and at the other end with an intermediate point along said source of potential in said output circuit, said auxiliary circuit being inductively coupled with said input circuit whereby radio frequency signaling energy impressed upon said input circuit is amplified by the cooperative action of said first mentioned anode, cathode and control electrode and delivered to said auxiliary circuit for reduction in the requency thereof and the signaling energy at reduced frequency is impressed upon said input circuit for actuating said responsive device.

4:. A signal receiving circuit comprising in combination an electron tube having an I evacuated vessel, a pair of anodes, a cathode,

and a control elect-rode, an input circuit in terconnecting said control electrode and said cathode, an output circuit interconnecting one of said anodes and said cathode, said output circuit including a responsive device and an auxiliary circuit connected between said other anode and a point of high potential in said output circuit and having high frequency and low frequency windings connected therein and inductively coupled with said output and input circuits, respectively, for effecting amplification of incoming signaling energy at different frequencies and the rectification of the signaling energy for operation of said responsive device.

In testimony whereof I have hereunto affixed my signature this 15th day of December, 1922.

' SAMUEL COHEN. 

